The present invention is in the field of automatic transmissions; more particularly the present invention relates to an improved clutch plate for use in an automatic transmission of an automobile.
Automatic transmissions for automobiles comprise a housing, means within the housing to transmit the rotation and power from the motor to the driveshaft of the automobile. Power and rotation are transmitted in part via a series of engageable friction plates such as friction or clutch plates.
In a typical assembly, a clutch plate is mounted on a splined hub at the end of a rotatable shaft. The clutch plate is a circular disc having concentric hole. There are a plurality of teeth in plane of the disc extending from the inner circumference of the hole toward the center of the disc. The teeth are designed to match the space between the splines on the hub. As the hub rotates the clutch plate rotates with it. The clutch plate has two faces, a front face and a back face. Typically, a layer of friction-resistant material such as friction paper as is known in the art is located on both the front face and the back face between the inner and outer circumferences of the disc. Upon engagement at least one rotating friction plate is pressed against another surface of a rotatable article, i.e. a steel plate causing the steel plates to rotate. The rotation and power is transmitted from the rotating shaft through the clutch plate. A typical apparatus is made by the General Motors Corporation and is known as a GM TH 440-T4 ME-7 transmission. This is described at page 40 of Automatic Transmission Parts Catalog 1988, printed by Transmission Industry Publication, Inc., Fresno, Calif. (1987), hereby incorporated by reference.
In such transmissions the clutch plate is mounted on a splined hub. For a variety of reasons including the method to make the splined hub, the hub is usually made of a softer metal than the clutch plate disc. The hub can be made by deep-drawing cold-rolled steel. The hub is made of a steel such as SAE 1008 type steel, and the disc is typically made of steel such as SAE 1020 type steel. There is usually a small clearance space between the teeth of the disc and the spline of the hub. Upon initiation of rotation and engagement of the clutch, the edges of the disc teeth impact the surface of the splines. The differences in hardness between the hub and the disc, and the thinness of the disc result in the scoring and eventually cutting the splines. Total failure results when the hub is actually cut or sliced off by the teeth of the disc.